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1. Presentation By:
Arsalan Saeed Qureshi (D-16-TE-09)
Hamza Syed (D-16-TE-45)
Department Of Telecommunication Engineering

2. AGENDA
LED: How It
Works.
Types of LED.
Comparison.Applications.
Advantages &
Disadvantages.

3. HOW
IT
WORKS.
▪ When current flows across a diode, negative electrons move one way and
positive holes move the other way the wholes exist at a lower energy level
than the free electrons.
▪ Therefore when a free electrons falls it loses energy, so the energy is
emitted in a form of a photon, which causes light.
▪ The color of the light is determined by the fall of the electron and also
relies at the energy level of the photon.
Point 1 Point 2 Point 3
Light Emitting Diode

4. TYPES
OF
LED.
▪ Well LED’s are created in different variety of shapes and sizes. The color of the
plastic lens is sometimes same as the original color of light emitted.
▪ Modern high-power LEDs such as those used for lighting and backlighting are
generally found in Surface Mount Technology (SMT) (research yourself) Some of
the main types are given below:
▪ Traditional Inorganic LEDs - This type of LEDs manufactured from inorganic
materials like Aluminum Gallium Arsenide (AlGaAr), Gallium Arsenide
Phosphide (GaArP), and many more.
▪ Multi Color LEDs – Bi Color (Two Different Types).
▪ 1. One type consists of two dies connected to the same two color types of light.
▪ 2. Current flow in one direction emits one color, and current in the opposite
direction emits the other color.
▪ Organic LEDs - The OLED mostly used display technology like computer
monitors, television , mobile phone screen etc. (It contains Carbon and uses two
polymers or small molecule)
▪ Miniature – As the name says miniature LEDs are mini which means that they
are much smaller than a traditional 5mm of lamp type LED.
▪ High power – The high power LEDs are in series with a typical efficiency of 140
lm/W.

5. Comparison

6. Applications.
▪ LEDs are fall into three main categories:
1. Indicators and Signals - The low energy consumption, low maintenance
and small size of LEDs. They are used as status indicators and displays on
a variety of equipment and installations as well as stadium airports and
railway stations, trains, buses, trams, and ferries etc.
2. Lighting - LEDs are now used commonly in all market areas from
commercial to home use: standard lightning, stage, theatrical,
architectural, industrial and public installations, wherever artificial light
is required.
3. Data Communication & Other Signaling - Light can be used to transmit
data and analog signals. Listening device in many theaters and similar
spaces use arrays of infrared LEDs to send sound to listeners receivers.
Light-emitting diodes are used to send data over many types of fiber
optics cable, from digital audio the very high bandwidth fiber links that
form the internet backbone.

7. Advantages
&
Disadvantages.
▪ Advantages:
▪ Efficiency: LEDs emit more lumens per watt than incandescent light bulbs.
The efficiency of LED lighting fixtures is not affected by shape and size,
unlike fluorescent light bulbs or tubes.
▪ Color: LEDs can emit light of an intended color without using any color
filters as traditional lighting methods need. Easily available many colors.
▪ Size: LEDs can be very small smaller than 2 mm.
▪ On/Off time: LEDs light up very quickly. A typical red indicator LED will
achieve full brightness in under a microsecond.
▪ Cycling: LEDs are ideal for uses subject to frequent on-off cycling, unlike
incandescent and fluorescent lamps that fail faster when Highintensity
discharge lamps that require a long time before restarting.
▪ Lifespan: LEDs can have a relatively long useful life. One report estimates
35,000 to 50,000 hours of useful life, though time to complete failure
may be longer.
▪ Focus: The solid package of the LED can be designed to focus its light.
Incandescent and fluorescent sources often require an external reflector to
collect light and direct it in a usable manner.

8. Advantages
&
Disadvantages.
▪ Disadvantages:
▪ High initial price : LEDs are currently more expensive, price per lumen. In
2012, the cost per thousand lumens was about $6. The price was expected
to reach in 2013 $2/kilolumen and March 2014 $1.
▪ Light Quality: Most cool-white LEDs have spectra that differ significant
from a black body radiator like the sun or an incident light.
▪ Temperature dependency: Driving the LED hard in high ambient
temperatures may result to overheating of the led package ,eventually
leading to device failure.
▪ Voltage sensitivity: Typically, the forward voltage of an LED is between 1.8
and 3.3 volts. It varies by the color of the LED. A red LED typically drops
1.8 volts, but since both voltage drop and light frequency increase with
band gap, a blue LED may drop from 3 to 3.3 volts.

9. References.

10. Personal
Note.
If you want this slide or any other
slides related to your engineering
courses, you can go to
“www.slideshare.com” and search
Arsalan Qureshi for all the slides
including this one.

11. ?
THANK YOU SO MUCH
EVERYONE IT IS OUR
GREAT PLEASURE TO
SHARE OUR
KNOWLEDGE IN FRONT
OF YOU ALL. ALLAH
HAFIZ HAVE A NICE
DAY ☺